This patent application relates to wireless communications.
Wireless communication systems can include a network of one or more base stations and one or more relay stations to communicate with wireless devices. Each base station and relay station emits radio signals that carry data such as voice data and other data content to wireless devices. These radio signals can include additional information for communication management functions. Such additional information can include information to allow a wireless device to identify a cell sector of a base station and/or information to synchronize signaling in time and frequency. A wireless device may process the communication management information first before processing payload data.
Communication systems based on the orthogonality of frequencies of multiple subcarriers such as Orthogonal Frequency-Division Multiplexing (OFDM) and Orthogonal Frequency-Division Multiple Access (OFDMA) can achieve a number of potential technical advantages in wideband wireless communications such as resistance to multipath fading and interference. In wireless communication systems, a base station (BS) communicates with wireless device(s) in a service area. Wireless devices can include a mobile subscriber station (MSS), wireless station, or mobile station (MS).
A service area can be divided into multiple cells. The cells can be further divided into cell sectors. A BS's location can define a respective cell's service area in which the base station transmits to a wireless device via downlink (DL) radio signals. A wireless device can transmit information to a base station via uplink (UL) radio signals.
Multiple factors may limit the radio coverage area of a network of fixed base stations. Various structures may block the radio signals of one or more base stations. For example, a tall building may shield a particular area from a base station's radio signal, thus creating an undesired situation referred to as shadowing. At the edge of a cell, the signal strength can weaken. A weaker signal can lead to increased error rates of transmitted information or received information.
Adding additional base stations or relay stations can mitigate these limiting factors. Relay stations (RS) can be deployed among fixed base stations to relay communication signals between a mobile station and a base station. Relay stations can extend the coverage and improve the communication capacity and quality of a base station. A RS can be a fixed transceiver or a mobile transceiver station depending on the specific conditions for deploying such relay stations. A mobile station's signals can “hop” through one or more relay stations before reaching a serving base station. A mobile station can communicate with a relay station or directly with a base station.
A multi-hop relay wireless communication system, such as a multi-hop relay network in accordance with IEEE 802.16j, can include one or more MR base stations (MR-BS) and one or more relay stations. Multi-hop relay networks can operate in one of multiple modes, such as those modes defined by the IEEE 802.16j standard, to provide enhanced coverage and service to wireless devices. In these systems, radio resources, such as radio links and transmission slots on those radio links, can be scheduled and allocated centrally or distributed.
With distributed scheduling, the MR-BS and the relay stations independently determine and schedule the allocations of radio resources of their own radio links or channels and generate signaling messages according to the individual scheduling results.
With centralized scheduling, the MR-BS is responsible for performing resource allocation and scheduling of radio links under control of the MR-BS, such as radio links between BS and RS, RS and RS, BS and MS, and RS and MS. The MR-BS transmits an output of the scheduling to the relay stations. For example, a BS schedules radio link resources including access links of the BS (e.g., a link between a BS and a MS), relay links of the BS (e.g., a link between a BS and a RS), and access links and relay links of subordinate RSs. The BS can inform each subordinate RS of the scheduling result by using messages such as Mobile Application Part (MAP) messages.